1. Field of the Invention
The present invention relates to a recorder that records a file recording management table, prepared for managing digital data as a file, on a recording medium and a recording medium on which the file recording management table is recorded, and more particularly to a recorder that can quickly read information from, and write information to, a file management table and a recording medium on which the file recording management table is written.
2. Description of the Related Art
Optical discs used widely today are classified roughly into three types. The first is a ROM type disc from which data can only be read. This type of optical disc is used as a distribution medium of music and videos, and its representative example is a CD (Compact Disc) and a DVD-ROM (Digital Versatile Disc ROM). The second is an RW type disc to or from which data can be written or read repeatedly. This type of optical disc is used primarily by individual users for recording broadcasts, and its representative example is a DVD-RAM and a DVD-RW (DVD rewritable). The third is an R type disc to which data can be written once. The R disc is sometimes called a WORM type disc that is an abbreviation of Write Once Read Many. The R type disc, lower in cost as compared with an RW type disc, is used widely for saving video information, and its representative example is a CD-R (CD Recordable) and a DVD-R (DVD Recordable).
Data recorded on any of the above media is read by focusing a laser beam from an optical pickup, built in the disc drive unit, onto the disc surface and then interpreting the reflected beam. Data is recorded on an R type and an RW type recordable disc by controlling the intensity of laser radiation.
FIG. 1 shows the configuration of a standard optical disc recording/playback system. An optical disc drive 1 comprises an optical disc 2 to or from which data is recorded or played back, an optical pickup 3 for focusing a laser beam, a servo circuit 4 for controlling the position of the optical pickup for optimum recording and playback, a data processing circuit 5 for performing error correction coding and digital modulation for data to be recorded or played back, an interface 6 for converting data to allow a host (host computer) 8 to interpret data to be recorded or played back, and a drive control circuit 7 for controlling the whole system.
The host 8 is usually a personal computer to which not only the optical disc drive 1 but also other storage devices, such as a hard disk drive, are usually connected according to the interface standard common to the storage devices including the optical disk drive.
The host can treat an optical disc drive, on which a recording type disc is mounted, as if it was a string of recording blocks to and from which data can be written and read. A recording block (sector) can be specified by a numeric value called a logical address. The interface standard described above stipulates that the host issues a command, such as a read command and a write command, to the optical disc drive with a read/write start logical address and the number of transfer blocks specified and the transfer protocol for data that is recorded and played back.
Therefore, when the host 8 records generated data on a recording-type disc 2, the host 8 must first determine the write start logical address and the number of blocks in which data is to be written, issues a write command to the optical disc drive 1, and then sends recording data to the optical disc drive 1.
The optical disc drive 1 receives the recording data via the interface 6, performs error correction coding and modulation processing for the recording data via the data processing circuit 5, and drives the optical pickup 3 to write the recording data.
The disc 2 also has addresses written in advance on the whole recording surface for determining recording positions. Those addresses are generally called physical addresses. The drive control circuit 7 converts the recording start logical address, specified by the host 8, to an appropriate physical address and controls the positioning of the optical pickup 3 and the recording start time. This address conversion is usually made by a simple method, for example, by adding a constant offset to the logical address.
On such an optical disc, recording data is usually managed as a file. That is, to distinguish a sequence of recording data (one file) from another sequence of recording data (another file), the identification information on the sequence of recording data and the information on the recording position on the disc are recorded as file system data separately from the recording data. Although supplementary information on a file includes the data size and the recording date/time of the file, the most basic information representing a file is the file name that identifies the file and the extent information on the recording position of the file on the disc.
FIG. 2 shows an example of file system data that has been conventionally used. FIG. 2 shows the configuration of file system data according to the ISO/IEC 9293 standard. This file system data is composed of a FAT (File Allocation Table) including FAT items, each 12 bits or 16 bits long, and directory items (directory records DR (Directory Record)).
The recording data area is managed in units, called clusters, each of which is composed of multiple consecutive logical blocks on the disc. The FAT items are numbered sequentially in order of occurrence in the FAT with one FAT item corresponding to one cluster on the disc. The value of 0, if stored in the nth FAT item, indicates that data can be written in the nth cluster. A non-zero value in the nth FAT item indicates that file data is already written in the nth cluster on the disc. A non-zero value in a FAT item indicates either the number of the cluster in which the next file data is stored or a special value indicating that the corresponding cluster is the last cluster of the file data.
On the other hand, a directory record DR contains information on a specific file; that is, a directory record contains a file name that is file identification information and the number of a cluster in which the first data of the file is stored. This cluster number is used as a link to a FAT item.
Therefore, in the example shown in FIG. 2, the recorder/player reads the directory record DR, recognizes the file name, and recognizes that the first cluster of the file is cluster 98. After that, the recorder/player reads the 98th FAT item and recognizes that the next cluster, in which the next file data is recorded, is cluster 100. Next, the recorder/player reads the 100th FAT item and, upon detecting that the item contains a special value (4095 in this example), recognizes that the cluster 100 is the last cluster of the file. In this way, the recorder/player reads the file system data and identifies a file recorded on the disc.
The file system data recording method described in this “Description of the Related Art” satisfies the need to have the recorder/player recognize a file name and the recording area of the file recorded on the recording medium. However, this method requires both a FAT item and a directory record DR to get file information composed of a file name and its recording area.
Because the FAT items and directory records DR are usually recorded in different positions on a disc, the optical pickup must be moved on the disc to allow the recorder/player to read this information. The optical pickup movement operation, called a seek operation, consumes relatively a long time, resulting in the problem that it takes long until the recorder/player completes reading the file system data.
In addition, when the file system data is updated as a file is added or an existing file is updated, both the FAT items and the directory records DR must also be updated. During this update, the write operation involves the seek operation that consumes time in updating the file system data.